Teenagers
If you have teenagers
They are not a liability in an emergency. They are the second adult.
The honest version
Their real vulnerability is the phone, and not for the reason you think.
Give them a real role
Charging duty, radio duty, checking on an elderly neighbour. Teenagers who have been given responsibility behave extremely well and remember it for life.
Teach the three questions
Who is telling me this, when did it happen, and what am I being asked to do. Teenagers are the most targeted group for rumour and recruitment during any incident, in every country we cover.
A power bank each
Cheaper than the argument. It also means the household is not down to one working phone.
Agree a meeting point they would actually go to
Not the church hall you have never been in. The place they already go.